Multi-fiber loop back plugs are used to facilitate testing fiber optic systems. Multi-fiber loop back plugs are used to loop back test signals such that the test signals can be transmitted and received from a single location. United States Patent Application Publication No. 2006/0257092 discloses a multi-fiber loop back plug adapted to be optically and mechanically coupled to a fiber optic connector. The multi-fiber loop back plug includes a ferrule having a connector interface side that engages an interface side of a ferrule of the fiber optic connector when the multi-fiber loop back plug and the fiber optic connector are coupled together. The multi-fiber loop back plug also includes a plurality of loop back optical fibers defining loop back paths. The loop back optical fibers have end portions supported by the ferrule of the multi-fiber loop back plug. The end portions of the loop back optical fibers have end faces that are aligned in a row at a connector interface side of the ferrule of the multi-fiber loop back plug.